Optical and electrical properties of ultrasonic spray pyrolysized p-CdTe films

The p-CdTe films are prepared on thoroughly cleaned glass substrates by using ultrasonic spray pyrolysis techniques in-situ reducing atmosphere with air-ambient at 548 and 573 K. The resultant films are characterized by using X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray (EDAX) analysis, UV-Visible spectroscopy and Hall measurement set-up. The characterization studies revealed crystallization of the main p-CdTe phase with minor oxidation corresponding to TeO₂ in resultant films. The uniform size distribution of spherical particles with average particle size = 0.2 μm is noted from SEM studies. The optical properties are found to be absorbance (α) = 0.80 and band gap (E_g) = 1.46 eV for the films prepared at 573 K. The less oxidation at higher processing temperature realized in XRD and EDAX studies might be due to higher crystallization rate of p-CdTe dominating the oxidation. The Hall coefficient, R_H = 0.0205 × 10⁴ cm³/C, resistivity, r = 0.5812 × 10² Ω-cm and negative current value in Hot probe experiment indicated p-type semiconductor nature of resultant films processed at 573 K. The higher concentration (n), and less mobility (μ) of majority charge carriers for the films processed at 573 K might be due to less oxidation at higher temperature.